Tribological properties of PVD tool coatings in forming operations of steel sheet

In this work, the tribological properties of tool coatings applied by physical vapour deposition are studied. A first aspect is the resistance to galling and abrasive wear, which are investigated by means of a flat/cylindrical multifrottement test. The observations for the evolution of the friction coefficient discriminate the various coatings as regards the onset of galling. In addition, topographic inspection of the tools and the steel strips yields crucial information about galling scratches and wear tracks supporting a possible quantitative ranking of the different tribological systems. Subsequently, the effect of tool coatings in laboratory deep drawing operations is considered. The modification of the tribological conditions by applying a coating to the tool has a striking influence on the feasibility window to make cups. These observations are described in detail, while also the correlation with the roughness of the coated tools is briefly discussed.